Coordinate Measuring Machines (CMM) are used in the art of dimensional metrology and are known in the art. In many cases the CMM comprises a reference surface, for example a rectified granite plane on which the workpieces to be measured can be placed, and a movable support that can be precisely positioned in the three coordinates XYZ by a suitable assembly of actuators and encoders.
Coordinate probe mounted on CMM could be a simple touch trigger probe, which determines the instant in time of the contact, as described, for example in EP1610087. In other cases, particularly when the surface is scanned with a probe in continuous contact, it is known to use a probe that determines the amount of deflection of the stylus in 3-D, for example by an LVDT or strain-gauge sensor, and transmits this deflection to the controller, to be integrated in the coordinate calculation.
Among the optical probes that can be used in CMM are micro-imaging digital systems, which are moved like the mechanical measuring probes, and are aimed at the point whose coordinates are to be measured, instead of touching the material, allowing 3-D coordinate measurements. Laser coordinate probes can likewise be used which are able to determine the coordinate of points on the surface of a measured object as they are illuminated by a scanning laser beam.
Coordinate measuring systems having a rotating adapter for measuring probes are known in the art. EP2384851 discloses a CMM comprising a moveable support and a modular rotational fitting arranged to interoperate between such moveable support and a probe connector. This modular rotational fitting comprises a plurality of electrical and optical signal connections and an actuator to turn the rotation fitting up to a predefined angle.
EP1963781 discloses a scanning system comprising a continuously rotating optical scan sensor. The scan probe comprises an optical slip ring that includes a fluid mounted light transport module in order to assure the transmission of optical signals between the scan sensor and the scanning system.
However, measurement systems of the prior art have limitations in selection of probes, in the static and dynamic geometrical errors, in the maximum scanning speed that can be achieved and, in many cases, they are unsuitable to continuously rotate contact and optical measuring probes around the rotational axis, without sacrificing coordinate precision. Known coordinate measuring systems suffer, at high scanning speed, of the vibrations generated by masses in rapid oscillatory movement. These vibrations are a source of measuring errors that are difficult to isolate and to quantify from the sampled points. Another limitation of the known coordinate measuring systems is an inability to offer a large selection of probes, including contact and optical probes, having different dimensions, in order to measure complex pieces. Moreover, the use of long and massive probes further increases the measuring error of such measuring systems.
US2011/270570 discloses a limited rotational probe support for CMM that could be modified to provide continuously rotations.
US2014/101953 and US2006/016086 disclose manually operated articulated arm CMM whose rotational segments and joints comprise optical and/or electrical slip rings.